A composition that softens at a predetermined temperature between about 20oC and about 62oC, comprising at least one block copolymer having at least two thermal transition temperatures. The composition is characterized by at least two thermal transition temperatures, one of which is a predetermined lower...https://www.google.com/patents/WO1986003980A1?cl=en&utm_source=gb-gplus-sharePatent WO1986003980A1 - Compositions that soften at predetermined temperatures and the method of making same

Compositions that soften at predetermined temperatures and the method of making sameWO 1986003980 A1

Abstract

A composition that softens at a predetermined temperature between about 20oC and about 62oC, comprising at least one block copolymer having at least two thermal transition temperatures. The composition is characterized by at least two thermal transition temperatures, one of which is a predetermined lower transition temperature between about 20oC to about 62oC and one of which is an upper transition temperature above about 62oC. The composition has the physical properties of a rigid, crystalline or glassy polymer below the predetermined transition temperature and the physical properties of a flexible, rubbery polymer at and above the predetermined transition temperature, but below the upper transiiton temperature. In a preferred embodiment, the composition of the present invention further comprises a plasticizer or polymer that has at least one thermal transition temperature and is thermodynamically compatible with at least one block of the block copolymer. For most biomedical applications, the composition of the present invention has a predetermined glass transition temperature at or near body temperature. The present invention also provides a method of making the composition, a method of making biomedical devices and materials and articles with shape-memory properties from the composition, and biomedical devices and materials and articles with shape-memory properties made from the composition.

Claims(OCR text may contain errors)

WHAT IS CLAIMED IS:

1. A composition that softens at a predetermined temperature, comprising at least one block copolymer, said composition characterized by at least two thermal transition temperatures, one of said transition temperatures being a predetermined lower transition temperature in the range of from about 20°C to about 62°C, the other of said transition temperatures being an upper transition temperature above about 62°C, said composition further characterized by the physical properties of a polymer selected from the group consisting of rigid, glassy polymers and rigid, crystalline polymers, below said predetermined transition temperature and the physical properties of a flexible, rubbery polymer at and above said predetermined transition temperature but below said upper transition temperature.

2. A composition according to Claim 1, further comprising a material selected from the group consisting of polymers and plasticizers that are thermodynamically compatible with at least one block of said block copolymer.

3. A composition according to Claim 1 or 2 , wherein said predetermined transition temperature is in the range from about body temperature to about 62°C.

4. A composition according to Claim 1 or 2, wherein said predetermined transition temperature is at about body temperature.

5. A composition according to Claim 1 or 2, wherein in the dry state at a temperature below about body temperature said composition is characterized by the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers, and in the hydrated state at about body temperature to about 62ºC said composition is characterized by the physical properties of a flexible, rubbery polymer.

6. A composition according to Claim 2 , wherein said block copolymer has an upper and lower thermal transition temperatμres, and said thermodynamically compatible material has at least one thermal transition temperature, wherein said lower transition temperature of said block copolymer and said transition temperature of said thermodynamically compatible material combine to form said predetermined transition temperature of said composition.

7. A composition according to Claim 6, wherein said lower transition temperature of said block copolymer is below said predetermined transition temperature of said composition and said thermal transition temperature of said thermodynamically compatible material is above said predetermined transition temperature of said composition.

8. A composition according to Claim 2, wherein said thermodynamically compatible material is selected from the group consisting of polyvinylchloride, styreneacrylonitrile copolymers, polyhydroxyethers, polycarbonates, polyesters, polyethers, nitrocellulose, cellulose derivatives and polystyrene.

9. A composition according to Claim 1 or 2, wherein said block copolymer is selected from the group consisting of block copolymers having a polyester block, block copolymers having a polyether block, and polyurethane/ureas.

10. A composition according to Claim 1 or 2, wherein said block copolymer is selected from the group consisting of polyester urethanes, polyether urethanes, polyurethane/ureas, polyetherpolyamides, and polyether polyesters.

19. A composition according to Claim 18, wherein said composition comprises about 40 to 60 weight percent of said phenoxy resin and about 60 to 40 weight percent of said polyester urethane.

20. A composition according to Claim 1 or 2, wherein said composition is blood compatible.

21. A method for making a composition that softens at a predetermined temperature, comprising the step of selecting a block copolymer having an upper and lower thermal transition temperature, such that said composition is characterized by at least two thermal transition temperatures, one of said transition temperatures being a predetermined lower transition temperature in the range of from about 20°C to about 62°C, the other of said transition temperatures being an upper transition temperature above about 62°C, and such that said composition is further characterized by the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers, below said predetermined transition temperature and the physical properties of a flexible, rubbery polymer at and above said predetermined transition temperature but below said upper transition temperature.

22. A method according to Claim 21, further comprising the steps of simultaneously blending together said block copolymer and a material selected from the group consisting of polymers and plasticizers that are thermodynamically compatible with at least one block of said block copolymer and having at least one thermal transition temperature, such that said lower transition temperature of said block copolymer and said transition temperature of said thermodynamically compatible material combine to form said predetermined transition temperature in the range of from about 20ºC to about 62°C, said blended block copolymer and thermodynamically compatible material imparting to said composition the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers below said predetermined transition temperature and the physical properties of a flexible, rubbery polymer at and above said predetermined transition temperature but below said upper transition temperature of said composition.

23. A method according to Claim 21 or 22, wherein said predetermined transition temperature of said composition is in the range from about body temperature to about 62°C.

24. A method according to Claim 21 or 22, wherein said predetermined transition temperature is at about body temperature.

25. A method according to Claim 21 or 22, wherein in the dry state at a temperature below about body temperature said composition is characterized by the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers, and in the hydrated state at about body temperature to about 62°C said composition is characterized by the physical properties of a flexible, rubbery polymer.

26. A method according to Claim 22, wherein said thermal transition temperature of said compatible block of said block copolymer is below said predetermined transition temperature of said composition and said thermal transition temperature of said thermodynamically compatible material is above said predetermined transition temperature of said composition.

27. A method according to Claim 21 or 22, wherein a radiopaque filler and a surface modifier are blended together with said block copolymer and said thermodynamically compatible material.

28. A method according to Claim 22, wherein said thermodynamically compatible material is selected from the group consisting of polyvinylchloride, styreneacrylonitrile copolymers, polyhydroxyethers, polycarbonates, polyesters, polyethers, nitrocellulose, cellulose derivatives and polystyrene.

29. A method according to Claim 21 or 22, wherein said block copolymer is selected from.the group consisting of block copolymers having a polyester block, block copolymers having a polyether block, and polyurethane/ureas.

30. A method according to Claim 21 or 22, wherein said block copolymer is selected from the group consisting of polyester urethanes, polyether urethanes, polyurethane/ureas, polyether polyamides and polyether polyesters.

31. A method according to Claim 27, wherein said surface modifier is selected from block copolymers having at least one block comprising polysiloxane.

32. A method according to Claim 27, wherein said radiopaque filler is selected from the group consisting of barium sulphate, bismuth subcarbonate, bismuth oxychloride, and tantalum.

33. A method according to Claim 21 or 22, wherein said composition. is blood compatible.

34. A method for making a biomedical device that softens at a predetermined temperature, comprising the step of forming into a biomedical device a composition comprising at least one block copolymer, said composition characterized by at least two thermal transition temperatures, one of said transition temperatures being a predetermined lower transition temperature at about body temperature to about 62°C, the other of said transition temperatures being an upper transition temperature above about 62°C, said composition further characterized by the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers, below about body temperature and the physical properties of a flexible, rubbery polymer at and above said predetermined transition temperature but below said upper transition temperature.

35. A method according to Claim 34, wherein said composition further comprises a material selected from the group consisting of polymers and plasticizers that are thermodynamically compatible with at least one block of said block copolymer.

36. A method according to Claim 34 or 35, wherein said predetermined transition temperature is at about body temperature and said biomedical device is a catheter.

37. A method according to Claim 34 or 35, wherein said predetermined transition temperature is at about body temperature and said biomedical device is a drug release device.

38. A method according to Claim 34 or 35, wherein said predetermined transition temperature is at about body temperature and said biomedical device is a thermal indicator.

39. A method according to Claim 34 or 35, wherein said predetermined glass transition temperature is in the range from about 10°C above body temperature to about 62°C, and said biomedical device is a material for making casts for broken limbs.

40. A method according to Claim 34 or 35, wherein said predetermined transition temperature is at about body temperature and said composition is formed into a catheter with shape-memory properties.

41. A method according to Claim 34 or 35, wherein in the dry state at a temperature below about body temperature said composition is characterized by the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers, and in the hydrated state at about body temperature to about 62°C said composition is characterized by the physical properties of a flexible, rubbery polymer.

42. A method according to Claim 35, wherein said thermodynamically compatible material is selected from the group consisting of polyvinylchloride, styreneacrylonitrile copolymers, polyhydroxylethers, polycarbonates, polyesters, polyethers, nitrocellulose, cellulose derivatives and polystyrene.

43. A method according to Claim 34 or 35, wherein said block copolymer is selected from the group consisting of block copolymers having a polyester block, block copolymers having a polyether block, and polyurethane/ureas.

44. A method according to Claim 34 or 35, wherein said block copolymer is selected from the group consisting of polyester urethanes, polyether urethanes, polyure- thane/ureas, polyether polyamides and polyether polyesters.

53. A method according to Claim 52, wherein said composition comprises about 40 to 60 weight percent of said phenoxy resin and about 60 to 40 weight percent of said polyester urethane.

54. A method according to Claim 34 or 35, wherein said composition is blood compatible.

55. A biomedical device made by the method of Claim 34 or 35.

56. A biomedical device formed from the composition, of Claim 1 or 2.

57. A method for making an article with shape-memory properties comprising the steps of heating a composition comprising at least one block copolymer, said composition characterized by at least two thermal transition temperatures, one of said transition temperatures being a predetermined lower transition temperature in the range of about 20°C to about 62°C, the other of said transition temperature being an upper transition temperature above about 62°C, said composition further characterised by the physical properties of a polymer selected from the group consisting of rigid, crystalline polymers and rigid, glassy polymers, below said predetermined lower transition temperature and the physical properties of a flexible, rubbery polymer at and above said predetermined lower transition temperature but below said upper transition temperature, to a temperature above said upper transition temperature, orienting said composition under stress into a first configuration, cooling said composition to below said predetermined lower transition temperature while said composition is in said first configuration, and cold forming said composition into a second configuration.

58. A method according to Claim 57, wherein said composition further comprises a material selected from the group consisting of polymers and plasticizers that are thermodynamically compatible with at least one block of said block copolymer.

59. A biomedical device formed from the composition of Claim 1 or 2 characterized by shape-memory properties.

60. A biomedical device with shape-memory properties made by the method of Claim 57 or 58.

61. An article formed from the composition of Claim 1 or 2 characterized by shape-memory properties.

62. An article with shape-memory properties made by the method of Claim 57 or 58.

Description(OCR text may contain errors)

COMPOSITIONS THAT SOFTEN AT PREDETERMINED TEMPERATURES AND THE METHOD OF MAKING SAME

Generally, the present invention relates to a composition that softens at a predetermined or selected temperature between approximately room temperature and approximately 62°C (about 25ºC above body temperature) but maintains good mechanical integrity well above that softening point, and the method of making said composition. The present invention also relates to biomedical devices and materials and articles with shape-memory properties made from said composition and the method of making said biomedical devices and materials and articles with shape-memory properties.

The composition of the present invention is ideally suited for biomedical uses and is especially suited for catheters. Because catheters are inserted into the body, the ideal catheter should have a high flexural modulus or stiffness similar to that of a hypodermic needle. This is particularly true for intravenous catheters which are inserted through the skin for a short distance and then inserted directly into a blood vessel. Since ease of insertion is a property that is most important in initially placing the catheter, intravenous catheters have always been made from high flexural modulus materials. Once the catheter is in place inside the vein, the stiff
property or high flexural modulus is a distinct disadvantage. High flexural modulus can result in irritation of the inner surface of the blood vessel by the tip of the catheter. As a result of the inflammatory irritation to the inside of the blood vessel, it is very common for these catheters to produce blood clots and become infected.

A very soft, rubber-like material would have much less tendency to irritate the inside of the blood vessel and would result in reduced morbidity and increased life of the catheter (the length of time before the catheter has to be replaced or moved to a different site). However, a flexible catheter would lack ease of insertion. Thus, there is a need for a catheter which is both easy to insert and does not irritate the inside of the blood vessel. The ideal catheter composition would have a very high modulus or stiffness upon insertion and would soften once inside the blood vessel.

It is an object of the present invention to provide compositions that soften at a predetermined or selected temperature between approximately room temperature and approximately 62°C (about 25°C above body temperature) but maintain good mechanical integrity above that softening point, and the method of making said composition.

It is another object of the present invention to provide biomedical devices and materials that soften at predetermined temperatures between about body temperature (37°C) and about 62°C (25°C above body temperature), and the method of making said biomedical devices and materials.

It is another object of the present invention to provide articles with shape memory properties that soften at
predetermined temperatures between about 20°C and about 62ºC, and the method of making said articles.

In general, the present invention provides a composition that softens at a predetermined temperature between about 20°C and about 62°C, comprising at least one block copolymer having at least two thermal transition temperatures, The composition has at least two thermal transition temperatures, one of which is a predetermined or selected lower transition temperature between about 20°C to about 62°C and one of which is an upper transition temperature above about 62°C. The composition has the physical properties of a rigid, glassy or crystalline polymer below the predetermined transition temperature and the physical properties of a flexible, rubbery polymer above the predetermined transition temperature, but below the upper transition temperature. In a preferred embodiment, the composition further comprises a plasticizer of polymer that has at least one thermal transition temperature and is thermodynamically compatible with at least one block of the block copolymer.For most biomedical applications, the composition of the present invention has a predetermined glass transition temperature at or near body temperature. The present invention also provides a method of making the composition and a method of making biomedical devices and materials and articles with shape-memory properties from the composition. The present invention further provides biomedical devices and materials and articles with shape-memory properties made from the composition.

In a first embodiment of the present invention, the composition comprises at least one block or segmented copolymer having a lower thermal transition temperature (either a glass transition temperature (Tg) or a melting point (Tm) ) between about 20ºC and about 62°C and nn
upper thermal transition temperature (either a Tg or Tm) above about 62°C. A major volume fraction of the block copolymer should have a lower transition temperature between about 20ºC to about 62°C to ensure the necessary drop in flexural modulus when the composition passes through the lower transition temperature. The major volume fraction of the block copolymer must also have the physical properties of a rigid, glassy or crystalline polymer below the lower transition temperature and the physical properties of a flexible, rubbery polymer at and above the lower transition temperature but below the upper transition temperature.

In another embodiment of the present invention, the composition comprises at least one block copolymer and a material that is selected from the group consisting of plasticizers and polymers that are thermodynamically compatible with at least one block of said block copolymer. Other blocks or segments of the block copolymer base are thermodynamically incompatible with the plasticizer or second polymer. The plasticizer or second polymer has at least one thermal transition temperature, (either a Tg or Tm) and the block copolymer base has at least two thermal transition temperatures.

The block copolymer or segmented copolymer is the base polymer of the composition. The plasticizer or second polymer is blended together with the base polymer. The compatible blocks of the base polymer and the plasticizer or second polymer form a miscible blend with a transition temperature between the thermal transition temperature of the compatible block of the base polymer and the thermal transition temperature of the plasticizer or second polymer. The transition temperature of the miscible blend may be varied by varying the relative amounts of the two components. The blocks or segments of the base
polymer which are incompatible with the plasticizer or second polymer should have a Tg or Tm higher than the temperature range to be encountered in the end use of the composition of the present invention. The incompatible block of the base polymer will have a Tg or Tm in the composition very close or equal to the Tg or Tm it had in the unblended base polymer.

At temperatures above the predetermined transition temperature of the composition, the blend will be analogous to a thermoplastic elastomer with a soft block transition temperature that may be varied over a wide range of temperatures. The temperature range over which the transition takes place will narrow if the two miscible components are highly compatible, producing an abrupt change in the mechanical, thermal, transport, electrical, and other properties of the blend as the temperature is raised or lowered through the transition temperature.

The properties of the blend at temperatures above and below the predetermined transition temperature can be varied considerably by varying the composition of the base polymer. Greater concentration of the miscible or compatible block in the base polymer will result in a greater proportion of the blend subsequently possessing the predetermined transition temperature of the composition. For instance, in a 60/40 blend of a polycaprolactone (PCL) /diisocyanatodiphenylmethane (MDI) /butanediol (BD) polyurethane base polymer and phenoxy resin, the soft block PCL concentration of the base polymer may be varied. At very low PCL concentration, the blend will be very rigid below the predetermined transition temperature and will soften little when heated above the predetermined transition temperature. At high PCL concentration
in the base polymer, the blend will soften dramatically above the predetermined transition temperature.

Similarly, the incompatible blocks or segments of the base polymer may be chosen to vary the properties of the blend. A hard block composed of hexamethylenediisocyanate and butanediol would have a lower transition temperature than a rigid block of diisocyanatodiphenylmethane and butanediol within the range of end use temperatures.

The compatible block or blocks in the base polymer and the second polymer or plasticizer have special requirements relative to each other. In addition to being thermodynamically compatible as determined by a single transition temperature for the blend, the block copolymer (base polymer) and plasticizer or second polymer are selected such that the lower transition temperature (Tg or Tm) of the block copolymer is different than the transition temperature (Tg or Tm) of the plasticizer or second polymer, one of the transition temperatures being higher and one lower than the desired or predetermined transition temperature of the composition. Generally, the compatible block of the base polymer will have the lower Tg or Tm and the second polymer will have the higher Tg or Tm. As the second polymer is added to the base polymer, the Tg or Tm of the soft block or segment of the base polymer increases. However, it is also possible to use a higher Tg or Tm base polymer with two hard blocks only one of which is compatible with the lower Tg or Tm plasticizer. As the lower Tg or Tm plasticizer or second polymer is added to the base polymer, the Tg or Tm of the compatible block of the base polymer decreases. In both cases, the relative amount of the second polymer or plasticizer will determine the final Tg or Tm of the compatible block of the
base polymer and accordingly, the predetermined thermal transition temperature of the blend.

The composition of the present invention is further characterized by the physical properties of a rigid, glassy, semi-crystalline, or crystalline polymer below the predetermined transition temperature and the physical properties of a soft, rubbery polymer at and above the predetermined transition temperature, but below the upper transition temperature of the composition. The physical or mechanical properties of glassy or crystalline polymers and rubbery polymers are described in "Mechanical Properties of Polymers and Composites," L.E. Nielsen, Dekker, N.Y. (1974) , and "Properties of Polymers, Their Estimation and Correlation with Chemical Structure," D. W. Van Krevelen, Elsevier, N.Y. (1976) , and are well known to those skilled in the art.

For biomedical uses, a preferred embodiment of the composition of the present invention has a predetermined glass transition temperature between about body temperature and about 62°C. For certain biomedical applications, such as making catheters, drug release devices, or thermal indicators, a preferred embodiment of the composition has a glass transition temperature at or near body temperature.

Accordingly, for certain biomedical applications, a preferred embodiment of the composition of the present invention is characterized by the physical properties of a rigid, glassy or crystalline polymer in the dry state at a temperature below about body temperature (preferably at a temperature between about 25 - 35 ºC or below) and is characterized by the physical properties of a flexible, rubbery polymer in the hydrated state at about body temperature to the next transition temperature which
should be above at least about 50°C, preferably above about 62°C.

For biomedical applications, a preferred composition of the present invention comprises at least one block copolymer and a second polymer thermodynamically compatible with at least one block of said block copolymer, wherein the block copolymer is characterized by at least two thermal transition temperatures, one being below about body temperature and the other being well above body temperature, preferably above about 62°C. The second polymer has at least one transition temperature (either a Tg or Tm) above body temperature.

The block copolymer (base polymer) is selected from the group consisting of polyester urethanes, polyether urethanes, polyurethane/ureas, polyether polyamides, polyether polyesters, and any other block or segmented copolymers containing at least one polyether or polyester block or segment. One preferred block copolymer (base polymer) is a polyester urethane. Polyester urethanes have glass transition temperatures of about -50°C to

-10ºC and about 100°C to 150°C. Another preferred block copolymer is a polyether urethane. Polyether urethanes have glass transition temperatures of about -85°C to -40ºC and about 100ºC to 150°C.

The second polymer is preferably selected from the group consisting of polyvinylchloride, styrene/acrylonitrile copolymers, polyhydroxyethers, polycarbonates, polyesters, polyethers, nitrocellulose, cellulose derivatives, and polystyrene. A preferred second polymer is the polyhydroxyether of bisphenol-A and epichlorohydrin (phenoxy resin). The phenoxy resin has a glass transition temperature of about 98ºC.
The two polymers are then blended in a ratio so that the predetermined lower transition temperature for the composition will be at or near body temperature or slightly above body temperature if hydration lowers this glass transition temperature further.

When used for catheters or other biomedical applications, the composition of the present invention may also contain a minor amount of a surface modifying additive. The surface modifying additive reduces the coefficient of friction and increases blood compatibility of the composition. In addition, radiopaque fillers may be used in the composition to render the catheters visible by fluoroscopy. Surface modifying additives may be selected from the group consisting of block/segmented multipolymers containing polysiloxanes or polyfluorocarbons as one block. Preferred surface modifiers are selected from the group consisting of polysiloxane/polyester block copolymers and polysiloxane/polyurethane copolymers. A more preferred surface modifier is a polysiloxane/polyester block copolymer, Radiopaque fillers may be selected from the group consisting of barium sulphate, bismuth subcarbonate, bismuth oxychloride, tantalum and other non-corrosive metals. A preferred radiopaque filler is barium sulphate.

Although the composition of the present invention has many biomedical applications, a preferred use for the composition is for catheters. For use as a catheter, a preferred embodiment of the composition has a glass transition temperature at or near body temperature, such that when the composition is at room temperature, it is below its glass transition temperature and is stiff and rigid, having the physical properties of a glassy or crystalline polymer. Accordingly, a catheter made of the composition will be easy to insert through the skin and
not the blood vessel. As the composition warms to body temperature, it will go through the transition and its flexural modulus will be decreased by about one to three orders of magnitude, causing the composition to soften considerably. Thus, while in the blood vessel the catheter will have less tendency to irritate the inside of the blood vessel and thus, less tendency to cause blood clots and become infected.

Because most intravenous catheters have thin walls, they have a tendency to heat up very quickly when exposed to a new temperature. As a result, the catheter can actually begin to soften as it is being inserted into the body, making insertion difficult. Therefore, a more preferred embodiment of the composition of the present invention has a predetermined lower thermal transition temperature slightly above body temperature . When the catheter is inserted into the body, the composition absorbs water from the blood and becomes plasticized; its predetermined lower transition temperature is lowered from slightly above body temperature to just below body temperature. The composition then goes through its transition to become a rubbery, flexible solid.

Another use for the composition of the present invention is for making contact lenses that soften at or near body temperature in the hydrated state. At room temperature, the composition would have a high flexural modulus and therefore could easily be machined into lenses. Once put in place in the eye, the composition would heat up, absorb water, pass through its predetermined lower transition temperature and become soft, flexible, and comfortable for the wearer and more permeable to gases, such as oxygen and carbon dioxide.
For other biomedical applications, a preferred embodiment of the composition of the present invention will have a predetermined lower transition temperature above body temperature but below about 62°C and an upper transition temperature above about 62°C, such that the composition has the physical properties of a rigid, glassy or crystalline polymer at about body temperature and the physical properties of a flexible, rubbery polymer at about 10ºC above body temperature to just below the upper transition temperature.

An example of a biomedical use for this preferred embodiment of the composition of the present invention is for making a material for constructing casts for broken limbs. The composition can be formed into a biomedical tape which can be softened by warming it to its predetermined lower transition temperature in hot or warm water or with a heat gun. When it becomes soft and flexible, it can be used to wrap a broken limb that has just been set. As the material cools to room temperature, it goes through the lower transition and becomes virtually as rigid as Plaster of Paris. The material remains rigid at body temperature to at least bathing temperature. The composition may replace Plaster of Paris as a material for constructing casts.

Another use for the composition of the present invention is for making articles with shape-memory properties that change shapes at a predetermined transition temperature in the range of about 25°C to about 62°C. For example, the composition can be heated to a temperature above its upper transition temperature, oriented under stress into a specific shape (configuration #1) then cooled while in that configuration #1 to below the lower predetermined or selected transition temperature of the composition. The composition can then be cold formed into another shape
(configuration #2) at that temperature, When the composition is heated to a temperature above the lower predetermined transition temperature but below the upper transition temperature, it will spontaneously reassume configuration #1.

Thus, for instance, a catheter with shape-memory properties could be made from the composition of the present invention. The composition could be formed into a catheter in one configuration above its upper transition temperature then cooled to below a lower transition temperature at or near body temperature and formed into a second configuration (e.g., a straight configuration). Upon insertion into the body, the catheter would warm to body temperature (its lower glass transition temperature) and reassume its first configuration.

Another use for the composition of the present invention would be for the production of toys with shape-memory properties . The composition could be oriented under stress into one toy shape above the composition's upper transition temperature. When cooled below the predetermined lower transition temperature, the toy could be reshaped by children. Then, the toy could be warmed to above its predetermined lower transition temperature, thus reassuming its original shape.

The present invention also contemplates the method of making a composition that softens at a predetermined temperature. One embodiment of the method of the present invention comprises the steps of selecting the desired thermal transition temperature and then preparing a block copolymer that has at least two thermal transition temperatures, one of said transition temperatures being a lower transition temperature equal to the predetermined or selected transition temperature of the composition and
the second transition temperature being well above that transition temperature. A major volume fraction of the block copolymer should have a transition temperature equal to the predetermined lower transition temperature for the composition in order to achieve the desired degree of softening as the composition passes through the predetermined lower thermal transition temperature. Preferably, the predetermined lower transition temperature of the composition is In the range of about 20°C (near room temperature) to about 62°C (about 25ºC above body temperature) and the upper transition temperature is above about 62°C.

For biomedical applications, it is preferred that the predetermined lower transition temperature of the composition be between about body temperature (37°C) and about 62°C. For catheters and similar biomedical devices inserted into the body, it is preferred that the predetermined lower transition temperature of the composition be at or near body temperature.

The various blocks or segments of the block copolymer are selected such that the physical properties of the composition are that of a rigid, glassy or crystalline polymer below the predetermined lower transition temperature of the composition and that of a flexible, rubbery polymer at and above the lower transition temperature, but below the upper transition temperature.

A second embodiment of the method of the present invention comprises the steps of selecting the desired transition temperature for the composition, selecting or making a block copolymer such that said block copolymer has at least two thermal transition temperatures. The lower transition temperature of the block copolymer should be either above or below the predetermined or selected lower transition temperature of the composition. A plasticizer or second polymer that is thermodynamically compatible with at least one block of the block copolymer and that has at least one thermal transition temperature (either a Tg or Tm) that is either above or below the predetermined transition temperature of the composition is selected or prepared, then blended together with the block copolymer such that the lower thermal transition temperature of the block copolymer and the thermal transition temperature of the compatible plasticizer or second polymer combine to form the predetermined lower transition temperature of the composition. The plasticizer selected for use in the composition of the present invention can be made by the method described in W. R. Sorenson and T. W. Campbell, Preparative Methods in Polymer Chemistry, Interscience Div. of John Wiley and Sons, N.Y., (1961), and G. Odian, Principles of Polymerization, McGraw-Hill, N.Y. (1970). The second polymer selected for use in the composition of the present invention can be made by the method described in W. F. Hale, Encyclopedia of Polymer Science and

Technology, 10,111 (1969), and H. Lee, D. Stoffey, and K. Neville, New Linear Polymers, McGraw-Hill, N.Y.,* (1967).
For biomedical uses, a surface modifier and/or a radiopaque filler can be blended together with the block copolymer in the first embodiment of the method of the present invention or with the base polymer and thermodynamically compatible plasticizer or second polymer in the second embodiment of the method.

The present invention also contemplates a method of making biomedical devices or materials that soften at a predetermined or selected temperature between about body temperature and about 62°C. In most applications, the predetermined softening temperature will be at or near body temperature. The method comprises the steps of making the composition of the present invention by either of the method embodiments discussed above, then forming it into a biomedical device or material. The composition of the present invention can be formed into a catheter, a drug release device, a thermal indicator, biomedical tape for constructing casts for broken limbs, contact lenses or many other biomedical devices.

The present invention is also directed to the biomedical devices or materials that soften at a predetermined temperature between about body temperature and about 62°C made by the method of the present invention or made with the composition of the present invention.

The present invention also provides a method of making articles with shape memory properties that soften at a predetermined temperature in the range of about 25°C to about 62°C, comprising the steps of making the composition of the present invention, heating said composition to a temperature above said composition's upper transition temperature, orienting said composition under stress into a first configuration, cooling said composition to below the predetermined lower transition temperature
while said composition is in said first configuration, and then cold forming said composition into a second configuration. The present invention also provides articles with shape-memory properties made according to the foregoing method or made from the composition of the present invention.

The following table indicates the decreasing flexural modulus of a preferred composition of the present invention for biomedical uses when it comprises various ratios of phenoxy resin and polyester urethane:

Phenoxy Resin/ Polyester Urethane Flexural Modulus [psi]

Wt/Wt 23ºC Dry 37°C Dry 37°C Hydrated

60/40 186400 159000 6729 50/50 160400 8950 602

40/60 93300 2867 1186

The flexural modulus data in the column designated "37ºC Hydrated" was obtained by measuring the composition's flexural modulus after one hour of hydration in 37ºC distilled water. The flexural modulus data in the two columns designated "Dry" was obtained by measuring the composition in its dry state at the designated temperatures. The following examples describe the tests from which this data was obtained and the preferred compositions of the present invention.

Example 1

A composition of the present invention comprising 60 weight percent of a resin comprised of the polyhydroxyether derived from bisphenol-A and epichlorohydrin (phenoxy resin) and 40 weight percent of a commercial polyester urethane (Estane 5707 produced by B.F.
Goodrich), in the form of compression molded sheets, was measured for flexural modulus in a thermal mechanical analyzer at 23ºC, 37ºC and at 37°C after an hour of hydration in distilled water. The flexural modulus of the composition at 23ºC was 186,400. The flexural modulus at 37ºC was 159,000 and the flexural modulus after one hour of hydration in 37°C distilled water was 6,729.

Example 2

A composition of the present invention comprising 50 weight percent of the phenoxy resin described in Example 1 and 50 weight percent of the polyester urethane described in Example 1, in the form of compression molded sheets, was measured for flexural modulus in a thermal mechanical analyzer. At 23°C, the composition had a flexural modulus of 160,400. At 37°C, the composition had a flexural modulus of 8,950 and after one hour of hydration in 37°C distilled water, the composition had a flexural modulus of 602.

Transition temperatures of each blend component separately and of the final composition were measured by differential scanning calorimetry (DSC) as follows:

The composition of the present invention comprising 40 weight percent of the phenoxy resin described in Example 1 and 60 weight percent of the polyester urethane described in Example 1, in the form of compression molded sheets, was measured for flexural modulus in a thermal mechanical analyzer. At 23ºC, the composition had a flexural modulus of 93,300. At 37°C, the composition had a flexural modulus of 2,867 and after one hour of hydration in 37°C distilled water, the composition had a flexural modulus of 1186.

Example 4

The composition of the present invention comprising 50 weight percent of the phenoxy resin described in Example 1 and 50 weight percent of a commercial polyether-based polyurethane (Estane 5714 produced by B.F. Goodrich) were melt blended and the transition temperatures were measured by differential scanning calorimetry (DSC) as follows:

Phenoxy resin: Tg = 91 ºC

Polyether-based polyurethane: Tg = -48°C

Blend (50% phenoxy resin/50% polyurethane) : Tg = 22°C

Additionally, 40 weight percent of the phenoxy resin, 40 weight percent of the polyether-based polyurethane, and 20 weight percent of a polydimethylsioloxane-polycaprolactone block copolymer surface modifier (36 weight percent polysiloxane) were melt blended. The transition temperature occurring around but below body temperature as measured by DSC was Tg = 5°C. This result indicates that the selected surface modifier is thermodynamically compatible with the base polymer and the second polymer.
Less surface modifier should be used to achieve a final Tg near 22 °C. Typically for biomedical applications, about 0.5 weight percent of a surface modifier would be used.